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Despite being one of the most destructive invasive species of ants, only two natural enemies are known currently for Wasmannia auropunctata, commonly known as the electric ant or little fire ant. Because viruses can be effective biological control agents against many insect pests, including ants, a metagenomics/next-generation sequencing approach was used to facilitate discovery of virus sequences from the transcriptomes of W. auropunctata. Five new and complete positive sense, single-stranded RNA virus genomes, and one new negative sense, single-stranded RNA virus genome were identified, sequenced, and characterized from W. auropunctata collected in Argentina by this approach, including a dicistrovirus (Electric ant dicistrovirus), two polycipiviruses (Electric ant polycipivirus 1; Electric ant polycipivirus 2), a solinvivirus (Electric ant solinvivirus), a divergent genome with similarity to an unclassified group in the Picornavirales (Electric ant virus 1), and a rhabdovirus (Electric ant rhabdovirus). An additional virus genome was detected that is likely Solenopsis invicta virus 10 (MH727527). The virus genome sequences were absent from the transcriptomes of W. auropunctata collected in the USA (Hawaii and Florida). Additional limited field surveys corroborated the absence of these viruses in regions where the electric ant is invasive (the USA and Australia). The replicative genome strand of four of the viruses (Electric ant polycipivirus 2, Electric ant solinvivirus, Electric ant virus 1, and Solenopsis invicta virus 10 (in the electric ant) was detected in Argentinean-collected W. auropunctata indicating that the ant is a host for these viruses. These are the first virus discoveries to be made from W. auropunctata.

Leaf-cutting ants are considered the most important herbivores in terrestrial environments throughout the Neotropics. Amoimyrmex Cristiano, Cardoso, & Sandoval, 2020 is the sister clade of the remaining leaf-cutting ants from the genera Atta and Acromyrmex. Amoimyrmex striatus was the only species cytogenetically studied within the genus and shares the same chromosomal number as Atta, bearing 22 chromosomes, whereas Acromyrmex bears 38 chromosomes, with the exception of the social parasite Acromyrmex ameliae (2n = 36). Our objective here was to cytogenetically analyze the species of Amoimyrmex bruchi and Amoimyrmex silvestrii, as well as to describe the karyotype of these sister species, using an integrative approach using classical and molecular cytogenetics. We aimed to characterize the cytogenetic markers that contribute to the systematics and taxonomy of the genus. Our results showed that the karyotypes of these two species are very similar, with an identical chromosome number (2n = 22), chromosome morphology (2K = 20m + 2sm), and location of 18S rDNA and telomeric repeat TTAGG on the chromosomes. However, the microsatellite probe GA(15) showed variation across the species and populations studied. We suggest that both species diverged relatively recently and are unmistakably sisters because of the many shared characteristics, including the highly conserved karyotypes.

Background The tawny crazy ant (Nylanderia fulva Mayr) is native to South America and was first reported in the continental United States (US) in 1938. It was not until the 1990s in Florida and 2000s in Texas that this ant was considered a serious pest in the US. Tawny crazy ant (TCA) is currently considered an invasive pest in six US states and this ant’s invasion success is attributed in part to a unicolonial nature, multiple queens per nest, natural enemies release in the invasive range, and ability to detoxify venom from other competitor ant species. A limited number of low-density molecular markers have previously shown little genetic differentiation among TCA populations across their geographic distribution in the US. Results Using High Throughput Sequencing (HTS) we obtained high-density molecular markers (i.e., SNPs) for TCA samples. With 26,657 SNPs we identified genetic variation among TCA populations in different states across the US (i.e., Texas, Louisiana, Alabama, Mississippi, Georgia, and Florida) and in South America (i.e., Argentina, Colombia, and Peru). Conclusion Our results underscore that for recently introduced invasive species, increasing the number of molecular markers used in population genetic studies can provide greater resolution. High-resolution information on regional genetic differences can help inform pest management strategies.

Linear infrastructures such as roads are among the most frequent generators of anthropogenic disturbances. Due to the expensive area that is affected along them, these great infrastructures represent a major conservation concern worldwide. Ants are an important component of natural ecosystems and are considered to be very sensitive to disturbance. The National Road Nº 150 is an important road of South America that forms part of the Central Bioceanic Corridor which will connect Brazil with Chile. In its trajectory, it crosses the Ischigualasto Provincial Park in Argentina. In order to evaluate the effects of this road on biodiversity in roadsides that run across this protected area, we compared species and functional group diversity of ants collected using pitfall traps between disturbed and undisturbed sites. In addition, we analyzed whether habitat variables, such as plant cover, gravel cover and soil hardness, explain ant species and functional group abundance in both site types. Twenty-one and 17 ant species were caught in disturbed and undisturbed sites, respectively. Roadside contained relatively more exclusives and rare species, while undisturbed sites harbored more common and dominant species. Hot climate specialists were more abundant at disturbed sites, whereas Opportunists at undisturbed sites. Ant species abundance seems to be positively influenced by gravel cover on roadside. In the present context of land use change, roadside could have an important function as reservoir and corridor for some ant species, and thus, plays a valuable role in the conservation of ant diversity in arid ecosystems.

Antagonistic interactions can affect population growth and dispersal of an invasive species. Wolbachia are intracellular endosymbiont bacteria that infect arthropod and nematode hosts and are able to manipulate reproduction, which in some cases leads to cocladogenesis. Moreover, the presence of the strictly maternally transferred Wolbachia in a population can indirectly induce selective sweeps on the hosts’ mitochondria. Ants have a Wolbachia infection rate of about 34%, which makes phylogenetic studies using mitochondrial markers vulnerable of being confounded by the effect of the endosymbiont. Nylanderia fulva is an invasive ant native to South America, considered a pest in the United States. Its distribution and biology are poorly known in its native range, and the taxonomic identity of this and its closely related species, Nylanderia pubens, has only recently been understood with the aid of molecular phylogenies. Aiming at estimating robust phylogenetic relationships of N. fulva in its native range, we investigated the presence and pattern of Wolbachia infection in populations of N. fulva from Argentina, part of its native range, to account for its possible effect on the host population structure. Using the ftsZ gene, 30 nests of N. fulva and four from sympatric Nylanderia species were screened for the presence of Wolbachia. We sequenced the MLST genes, the highly variable gene wsp, as well as glyQ, a novel target gene for which new primers were designed. Phylogeny of the ants was estimated using mtDNA (COI). We found supergroup A Wolbachia strains infecting 73% of N. fulva nests and two nests of Nylanderia sp. 1. Wolbachia phylogenetic tree inferred with MLST genes is partially congruent with the host phylogeny topology, with the exception of a lineage of strains shared by ants from different N. fulva clades. Furthermore, by comparing with Wolbachia sequences infecting other ants, we found that the strains infecting different N. fulva clades are not monophyletic. Our findings suggest there are three recent independent horizontally transmitted Wolbachia infections in N. fulva, and we found no evidence of influence of Wolbachia in the host mtDNA based phylogeny.

Species distribution models based on the correlation of bioclimatic variables and presence spatial data-points are useful for recognizing species habitat suitability. However, they have limitations in predicting the introduced ranges of invasive species that could be overcome by using species eco-physiological traits. By combining bioclimatic variables with thermal tolerance plasticity of the highly invasive little fire ant, Wasmannia auropunctata, we intend to better understand the mechanism underlying its current and future distributions. To this end, we performed: (1) laboratory physiological experiments to assess thermal tolerances (CTmin and CTmax) and evaluate the effect of acclimation (laboratory) and acclimatization (nature) on these variables, (2) behavioral foraging observations in the field, (3) a correlative and a simple mechanistic SDM. Briefly, physiological results showed a modulation of the CTmax and CTmin by different acclimation temperatures and by seasonal thermal acclimatization. In the field, worker foraging activity begins at environmental temperatures just above (less than 1 °C) the lowest CTmin recorded in the laboratory. At the global scale, CTmin constitutes a key physiological trait that, when linked with the minimum temperature of the coldest month, could explain the southernmost limit of W. auropunctata native distribution and its physiological capacity to expand in the Mediterranean region. The eco-physiological approach carried out here may help explain the current distribution and predict potential spread of populations when there is no certain information about the whole distribution of the species or under a changing environment. The latter is of great importance especially when analyzing invasive insects, pests or disease vectors.

Leaf-cutting ants (LCA) are considered one of the main herbivores and one of the most destructive pest insects of the Neotropics. Northeastern Argentina harbors the greatest species richness of these ants and in turn comprises the highest surface with forest plantations. Our aim was to establish which species of leaf-cutting ants are most commonly associated with forest plantations by analyzing their geographic distribution using published and unpublished species occurrence data. Also, estimate their potential areas of distribution along a latitudinal gradient that entirely encompasses northeastern Argentina using Ecological Niche Modeling. Only seven of the 20 species recorded were strongly associated with productive systems along the gradient, but only 2–3 species in each region could be considered high-risk species for forest plantations. High-risk species composition shows a turnover between regions. Our models show the potential distribution areas where LCA could become more abundant and dominant, and possibly causing a detrimental effect on the forest plantations in the studied region. We find that ecological niche models are useful tools to assess the environmental suitability of important LCA. Fil: Sánchez Restrepo, Andrés Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación para el Estudio de Especies Invasivas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Grupo de Investigación en Filogeografía y Filogenias Moleculares; Argentina Fil: Jiménez, Nadia Lis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación para el Estudio de Especies Invasivas; Argentina Fil: Confalonieri, Viviana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Grupo de Investigación en Filogeografía y Filogenias Moleculares; Argentina Fil: Calcaterra, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación para el Estudio de Especies Invasivas; Argentina

Ants, an ecologically successful and numerically dominant group of animals, play key ecological roles as soil engineers, predators, nutrient recyclers, and regulators of plant growth and reproduction in most terrestrial ecosystems. Further, ants are widely used as bioindicators of the ecological impact of land use. We gathered information of ant species in the Atlantic Forest of South America. The ATLANTIC ANTS data set-which is part of the ATLANTIC SERIES data papers-is a compilation of ant records from collections (18,713 records), unpublished data (29,651 records), and published sources (106,910 records; 1059 references), including papers, theses, dissertations, and book chapters published from 1886 to 2020. In total, the data set contains 153,818 ant records from 7,636 study locations in the Atlantic Forest, representing 10 subfamilies, 99 genera, 1,114 ant species identified with updated taxonomic certainty, and 2,235 morphospecies codes. Our data set reflects the heterogeneity in ant records, which include ants sampled at the beginning of the taxonomic history of myrmecology (the nineteenth and twentieth centuries) and more recent ant surveys designed to address specific questions in ecology and biology. The data set can be used by researchers to develop strategies to deal with different macroecological and regional-wide questions, focusing on assemblages, species occurrences and distribution patterns. Furthermore, the data can be used to assess the consequences of changes in land use in the Atlantic Forest on different ecological processes. No copyright restrictions apply to the use of this data set, but we request that authors cite this data paper when using these data in publications or teaching events.

An important goal of invasion ecology is to understand the colonization, establishment, and spread of exotic species. To accomplish this, it is essential to examine the ecology of introduced species in native populations. We examined organization patterns, spatial structure, and competitive abilities of ground-dwelling ants in different habitats of a protected area in east-central Argentina, where several highly invasive ant species naturally coexist, to determine whether all they are ecologically dominant in their native range as in their introduced range. We sampled ant communities at Otamendi Nature Reserve and found 49 ant species co-occurred with moderate separation among habitats, including five species that are global invaders; but only Solenopsis richteri (the most numerically dominant) and Linepithema humile (the best mass recruiter) were ecologically co-dominant along with another three non-invasive species in locally rich assemblages. Their co-occurrence was apparently facilitated by both niche and competitive differences. However, we found no evidence for discovery-dominance trade-offs, and ant diversity and spatial segregation suggested that competition only plays a secondary role in structuring assemblages in arboreal habitats. Despite L. humile and S. richteri were ecologically co-dominant, their hegemony was lower in the reserve than in their introduced range likely due to biotic resistance. The other invasive ants (Wasmannia auropunctata, Brachymyrmex patagonicus, and Nylanderia fulva) were not dominant. It is possible that their establishment, persistence, and high prevalence in anthropic habitats in native and introduced populations to be attributed to their better physiologic adaptations to disturbed habitats rather than to their superior competitive abilities. Fil: Calcaterra, Luis Alberto. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Sonia, Cabrera. Fundación para el Estudio de Especies Invasivas; Argentina Fil: Briano, Juan. Fundación para el Estudio de Especies Invasivas; Argentina

South American fire ant decapitating flies in the genus Pseudacteon (Diptera: Phoridae) are potential biocontrol agents of the invasive fire ants Solenopsis invicta and S. richteri in the United States and other regions of the world due to their high host specificity and the direct and indirect damage to their host ants. Despite their importance and the fact that several flies have already been released in the US, little is known about the genetic variability and phylogenetic relationships of Pseudacteon flies parasitizing South American fire ants in the Solenopsis saevissima species-group. A species delimitation analysis was conducted using a distance-based method (ABGD) and two tree-based methods (GMYC and mPTP) using COI sequences of 103 specimens belonging to 20 of the 22 Pseudacteon species known from southern South America. Additionally, phylogenetic relationships between the already described and new candidate species were inferred using mitochondrial (COI) and nuclear (wingless) sequences. The species delimitation analysis suggests that species richness in these flies has been previously underestimated, due to the existence of putative cryptic species within nominal Pseudacteon obtusus, P. pradei, P. tricuspis, P. cultellatus, and P. nudicornis. Geographic distribution and host fire ant species seem to support cryptic lineages, though additional morphological data are needed to corroborate these results. All phylogenetic analyses reveal that South American fire ant decapitating flies are grouped into two main clades, with Pseudacteon convexicauda sister and well differentiated relative to these clades. Neither host nor geographic association appeared to be related to the differentiation of these two main clades within South American fire ant decapitating flies. This work provides information that will allow testing whether the putative cryptic phorid fly species show differences in their effectiveness as biocontrol agents against the highly invasive imported fire ants.

The little fire ant Wasmannia auropunctata, native to the Neotropics, has become a serious pest worldwide over the past 100 years. It was originally distributed from Mexico to northern Argentina and new evidence suggests a recent southern range expansion during the last 60 years reaching central Argentina. This supercolonial ant species has a polymorphic reproductive system. Some populations, mostly found in undisturbed natural environments, are characterised by a classical sexual haplodiploid reproductive system. In other populations, which mainly occur in human-modified habitats, diploid queens and haploid males are produced clonally while workers are produced sexually. Here we studied the association between the recent southern range expansion of W. auropunctata in relation to human activity and clonality. We carried out an extensive survey within the southern limit of the species’ native distribution and characterised the type of habitat where populations were found. Moreover, we genetically determined the type of reproductive system in 35 populations by genotyping at 12 microsatellite loci a total of 191 reproductive individuals (i.e. queens and/or males). Clonality was the most common reproductive system, occurring in 31 out of 35 populations analysed. All the populations found in the recently colonised area in central Argentina were clonal and established in human-modified habitats, suggesting that clonality together with human activity might have facilitated the southwards expansion of W. auropunctata. Fil: Chifflet, Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Guzman, Noelia Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Rey, Oliver. Centre National de la Recherche Scientifique; Francia Fil: Confalonieri, Viviana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Calcaterra, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación para el Estudio de Especies Invasivas; Argentina

Background: Social insects are among the most serious invasive pests in the world, particularly successful at monopolizing environmental resources to outcompete native species and achieve ecological dominance. The invasive success of some social insects is enhanced by their unicolonial structure, under which the presence of numerous queens and the lack of aggression against non-nestmates allow high worker densities, colony growth, and survival while eliminating intra-specific competition. In this study, we investigated the population genetics, colony structure and levels of aggression in the tawny crazy ant, Nylanderia fulva, which was recently introduced into the United States from South America. Results: We found that this species experienced a genetic bottleneck during its invasion lowering its genetic diversity by 60%. Our results show that the introduction of N. fulva is associated with a shift in colony structure. This species exhibits a multicolonial organization in its native range, with colonies clearly separated from one another, whereas it displays a unicolonial system with no clear boundaries among nests in its invasive range. We uncovered an absence of genetic differentiation among populations across the entire invasive range, and a lack of aggressive behaviors towards conspecifics from different nests, even ones separated by several hundreds of kilometers. Conclusions: Overall, these results suggest that across its entire invasive range in the U.S.A., this species forms a single supercolony spreading more than 2000 km. In each invasive nest, we found several, up to hundreds, of reproductive queens, each being mated with a single male. The many reproductive queens per nests, together with the free movement of individuals between nests, leads to a relatedness coefficient among nestmate workers close to zero in introduced populations, calling into question the stability of this unicolonial system in which indirect fitness benefits to workers is apparently absent. Fil: Eyer, Pierre André. Texas A&M University; Estados Unidos Fil: McDowell, Bryant. Texas A&M University; Estados Unidos Fil: Johnson, Laura N. L.. Texas A&M University; Estados Unidos Fil: Calcaterra, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación para el Estudio de Especies Invasivas; Argentina Fil: Fernández, María Belén. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Shoemaker, Dewayne. University of Tennessee; Estados Unidos Fil: Puckett, Robert T.. Texas A&M University; Estados Unidos Fil: Vargo, Edward L.. Texas A&M University; Estados Unidos

Deforestation and over-grazing mediated by the humans have caused a serious process of desertification in the Argentine Monte Desert, which threats biodiversity of this ecosystem. Forests provide important resources and refuge for animal species, such as ants. The objective of this work was to survey the ant fauna of dryland forests of Ischigualasto Provincial Park, a protected area located in the hyper-arid Monte Desert ecoregion in the province of San Juan, Argentina. Ant species were surveyed in summer in three types of forests (Prosopis, Ramorinoa and Bulnesia forests), using a combination of sampling methods: pitfall-traps, baiting, and hand collection. A total of 33 ant species were collected, of which 17 are new records for the Monte Desert and Dry Chaco and 24 for the San Juan province. The species richness is within the range reported for other Argentine desert and semi-desert areas. Prosopis forest was the richest with 32 species (24 exclusive), followed by Ramorinoa and Bulnesia forests with 11 and 4 species, respectively. This study contributes to improve the knowledge of ant fauna in desert habitats of the world, especially those inhabiting Prosopis forests, which are the most important ant diversity hotspots within the hyper-arid desert. Fil: Amatta, Emilce del Valle. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina Fil: Calcaterra, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación para el Estudio de Especies Invasivas; Argentina Fil: Giannoni, Stella Maris. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina

Metagenomics and next generation sequencing were employed to discover new virus natural enemies of the fire ant, Solenopsis invicta Buren in its native range (i.e., Formosa, Argentina) with the ultimate goal of testing and releasing new viral pathogens into U.S. S. invicta populations to provide natural, sustainable control of this ant. RNA was purified from worker ants from 182 S. invicta colonies, which was pooled into 4 groups according to location. A library was created from each group and sequenced using Illumina Miseq technology. After a series of winnowing methods to remove S. invicta genes, known S. invicta virus genes, and all other non-virus gene sequences, 61,944 unique singletons were identified with virus identity. These were assembled de novo yielding 171 contiguous sequences with significant identity to non-plant virus genes. Fifteen contiguous sequences exhibited very high expression rates and were detected in all four gene libraries. One contig (Contig_29) exhibited the highest expression level overall and across all four gene libraries. Random amplification of cDNA ends analyses expanded this contiguous sequence yielding a complete virus genome, which we have provisionally named Solenopsis invicta virus 5 (SINV-5). SINV-5 is a positive-sense, single-stranded RNA virus with genome characteristics consistent with insect-infecting viruses from the family Dicistroviridae. Moreover, the replicative genome strand of SINV-5 was detected in worker ants indicating that S. invicta serves as host for the virus. Many additional sequences were identified that are likely of viral origin. These sequences await further investigation to determine their origins and relationship with S. invicta. This study expands knowledge of the RNA virome diversity found within S. invicta populations. Fil: Valles, Steven M.. United States Department Of Agriculture. Center For Medical Agric And Vet Entomology; Estados Unidos Fil: Porter, Sanford D.. United States Department Of Agriculture. Center For Medical Agric And Vet Entomology; Estados Unidos Fil: Calcaterra, Luis Alberto. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Fire is an important component of many natural ecosystems affecting plant communities and arthropods by mortality during combustion and/or indirectly through the modification of the habitat. The Iberá Natural Reserve (INR) is one of the most diverse ecosystems in northern Argentina; it is dominated by grasslands commonly affected by disturbances, such as grazing and fire. The objective of this work was to study the response of groundforaging ant assemblages, particular species, and functional groups to an extended fire of high intensity in four natural INR habitats with [5 years of cattle exclusion (strict conservation area). A total of 12,798 ant workers of 67 species were captured in 39 sampling stations. The ant fauna was less abundant in burned sites only a few days after the fire; 6 months later, no effect was detected. Richness and abundance of ants differed among unburned habitats. However, fire effect on species richness and composition remained unclear. The rapid recovery of the ant fauna made these insects poor indicators of long-term fire-promoted changes on biodiversity in open habitats dominated by grassland, though some ant species showed a high level of habitat fidelity mainly in unburned habitats. These results agree with those from other areas of the world, indicating that ants are particularly unreliable biodiversity indicators, with the exception of severe disturbance with long-term habitat restoration. Management decisions at the INR should be oriented to preserve the closed savanna, one of the most diverse and threatened habitat of Argentina. Fil: Calcaterra, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación para el Estudio de Especies Invasivas; Argentina Fil: Di Blanco, Yamil Edgardo. Centro de Investigaciones del Bosque Atlantico; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Nordeste. Instituto de Biologia Subtropical. Instituto de Biologia Subtropical - Nodo Puerto Iguazu; Argentina Fil: Srur, Malena. The Conservation Land Trust; Argentina Fil: Briano, Juan. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

The little decapitating fly Pseudacteon cultellatus Borgmeier (Diptera: Phoridae) from Argentina was released as a self-sustaining biological control agent against the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae) in Florida to parasitize small fire ant workers associated with multiple-queen colonies. This fly appears to be established at 2 of 5 release sites, but populations still remain very low (≤ 1% of total Pseudacteon flies) and localized more than 2 yr after their release. Further releases of P. cultellatus in the United States should be limited to a few additional sites in different habitats or climatic regions where this fly might be more successful.

Self-sustaining classical biological control agents offer hope for permanent wide-area control of imported Solenopsis fire ants in the United States because escape from abundant natural enemies left behind in Argentina is a likely reason for unusually high fire ant densities in the United States. The fire ant decapitating fly Pseudacteon obtusus Borgmeier (Diptera: Phoridae) was released as a biocontrol agent of the red imported fire ant (Solenopsis invicta Buren) in Gainesville, FL because it is a common parasitoid of this ant in Argentina and because it has a higher propensity of attacking fire ants along foraging trails than the two Pseudacteon species previously released. Field surveys of a rapidly expanding P. obtusus population (8‐12 km/yr) proved that this fly was capable of thriving and successfully competing with the much more abundant Pseudacteon curvatus Borgmeier. However, Pseudacteon tricuspis Borgmeier, the first decapitating fly released, was effectively excluded from most sample sites when faced with competition from both P. curvatus and the similar-sized P. obtusus. Despite clear evidence for competitive exclusion, P. tricuspis abundance at sample sites was positively correlated with the abundance of its two competitors— probably because of moderate to strong covariability in the suitability of sample sites for all three congeners. The addition of P. curvatus, the second parasitoid released, increased total parasitism pressure on fire ant populations by about 10-fold. The addition of P. obtusus, the third species, did not measurably improve total guild parasitism rates on imported fire ants in North Central Florida (as assessed by roadside trap counts), but the performance of this species will likely vary with habitat, region, and climate.

We studied radiation tolerance in queens of the red imported fire ant Solenopsis invicta Buren (Hymenoptera: Formicidae) to identify a dose that prevents reproduction. Virgin or fertile queens were collected from Santa Fe and Formosa provinces in Argentina and reared in the laboratory in microcolonies. Virgin queens were irradiated at 0 (control), 70, 90, 120, or 150 Gy, and fertile queens were irradiated at 0, 60, 125, and 190 Gy, and then followed for 11 wk in the microcolonies to evaluate survival and reproduction. Virgin queens lay trophic eggs that do not hatch, whereas fertile queens lay eggs that hatch and develop into brood. In general, queen oviposition and survival decreased with increasing irradiation dose. For virgin queens, no eggs were laid by irradiated queens after the third week, whereas the control queens continued laying eggs throughout the 11-wk experiment. For fertile queens, only one larva and no pupae was observed in the 60 Gy treatment and no larvae or pupae were observed in the 125 and 190 Gy treatments, whereas a total of 431 larvae and 83 pupae were produced by untreated control queens during 11 wks. Survivorship of virgin and fertile queens was similarly reduced by irradiation treatment. These results with S. invicta are consistent with previous findings for three other invasive ants, Wasmannia auropunctata (Roger), Pheidole megacephala (F.), and Linephithema humile (Mayr), that are hitchhiker pests on fresh horticultural commodities. A radiation dose of 150 Gy is proposed as a phytosanitary treatment to prevent reproduction in ants.

The evolutionary history of invasive species within their native range mayinvolve key processes that allow them to colonize new habitats. Therefore,phylogeographic studies of invasive species within their native ranges areuseful to understand invasion biology in an evolutionary context. Here weintegrated classical and Bayesian phylogeographic methods using mitochondrialand nuclear DNA markers with a palaeodistribution modelling approach, to infer the phylogeographic history of the invasive ant Wasmannia auropunctata across its native distribution in South America. We discuss our results in the context of the recent establishment of this mostly tropical species in the Mediterranean region. Our Bayesian phylogeographic analysis suggests that the common ancestor of the two main clades of W. auropunctata occurred in central Brazil during the Pliocene. Clade A would have differentiated northward and clade B southward, followed by a secondary contact beginning about 380 000 years ago in central South America. There were differences in the most suitable habitats among clades when considering three distinct climatic periods, suggesting that genetic differentiation was accompanied by changes in niche requirements, clade A being a tropical lineage and clade B a subtropical and temperate lineage. Only clade B reached more southern latitudes, with a colder climate than that of northern South America. This is concordant with the adaptation of this originally tropical ant species to temperate climates prior to its successful establishment in the Mediterranean region. This study highlights the usefulness of exploring the evolutionary history of invasive species within their native ranges to better understand biological invasions. Fil: Chifflet, Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Rodriguero, Marcela Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Calcaterra, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación para el Estudio de Especies Invasivas; Argentina Fil: Rey, Olivier. Institut National de la Recherche Agronomique; Francia. Centre National de la Recherche Scientifique; Francia Fil: Dinghi, Pablo Adrián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Baccaro, F. B.. Universidade Federal do Amazonas; Brasil Fil: Souza, J. L. P.. Instituto Nacional de Pesquisas da Amazônia; Brasil Fil: Follett, P.. Pacific Basin Agricultural Research Center; Estados Unidos Fil: Confalonieri, Viviana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

Irradiation is a postharvest quarantine treatment option to control ants and other hitchhiker pests on fresh horticultural products exported from Hawaii. The radiotolerance of the invasive little fire ant, Wasmannia auropunctata (Roger) (Hymenoptera: Formicidae: Myrmicinae), was studied to determine a dose sufficient for its control. Queens from each of five laboratory microcolonies started from five geographic locations in Argentina were irradiated at 20, 50, 70, or 100 Gy or left untreated as controls and then followed for 13 wk to observe colony growth. In general, queen survivorship, and the number of eggs, larvae, and pupae observed in the microcolonies decreased with increasing irradiation dose. In the 50-, 70-, and 100-Gy treatments, the number of eggs observed was reduced by 68, 66, and 76%, respectively, compared with untreated control microcolonies. The number of larvae in the 50-, 70-, and, 100-Gy treatments was reduced by 99.6%, and only one pupa was observed in the 50-Gy treatment and none in the 70- and 100-Gy treatments during the 13-wk experiment. Queens in the 100-Gy treatment had significantly reduced longevity compared with queens in the other treatments. Radiation doses ≥70 Gy stopped reproduction in W. auropunctata queens and should be sufficient as a phytosanitary treatment. Information from additional invasive ants in Myrmicinae and other subfamilies is needed before recommending a generic irradiation treatment for ants.

Parasitoid wasps of the genus Orasema Cameron have been considered as potential candidates for biological control of imported fire ants in the United States. Surveys were conducted for their occurrence in fire ant colonies across southern South America. In Argentina, 443 ant colonies were excavated at 57 sites and 11 positive sites were revisited to monitor the field persistence. In Paraguay, Bolivia and Uruguay, 288 colonies were examined in the field in 16 sites. Orasema simplex Heraty was the most abundant species, and found in 63.7% of the total parasitized colonies (n = 72). Orasema xanthopus (Cameron) and Orasema salebrosa Heraty were found at four sites in Argentina. In Bolivia, Orasema pireta Heraty was found at one site and parasitizing an unidentified Solenopsis species. Two new host species for Orasema were discovered, Solenopsis quinquecuspis Forel and Solenopsis macdonaghi Santschi. In addition, Orasema aenea Gahan was found parasitizing fire ants for the first time. The parasitoids persisted at 36.4% of the positive sites, most of them in rural habitats.

The maintenance of species diversity in modified and natural habitats is a central focus of conservation biology. The Iberá Nature Reserve (INR) protects highly diverse ecosystems in northeastern Argentina, including one of the largest freshwater wetlands in South America. Livestock grazing is one of the major disturbances to these ecosystems; however, its effect on ant diversity is poorly known. The objective of this work was to study the effect of savanna versus grassland and grazing on the structure and composition of subtropical terrestrial ants focusing on the particular response of the native red imported fire ant, Solenopsis invicta Buren. Unbaited pitfall traps were used to capture worker ants in 25 grazed and 20 nongrazed sites. Fifty ant species were collected. The savanna showed more species, individuals, biomass, and functional groups of ants than the grassland. S. invicta was the most frequently captured (61.4%) and numerically dominant species; however Camponotus punctulatus punctulatus Mayr showed the highest biomass. Grazing simplified vegetation structure in both habitats, but its impact on vegetation seemed only to promote a higher total biomass especially in the grassland, and/or functional groups, favoring occurrence of hot-climate specialists in the savanna. This study revealed that habitat type strongly affected the organization of the terrestrial ant assemblages at the INR. However, as in other studies, we did not find clear evidence that habitat modification by grazing significantly affected terrestrial ant assemblages. The weak grazing influence could be the consequence of the short enclosure time as to recover the original ant communities, the differential response of ant species to habitat type, and/or the resilience of ants.

The Iberá Nature Reserve in northeastern Argentina protects one of the largest freshwater wetlands and reservoirs of species in South America. However, key invertebrate groups such as the ants (Hymenoptera: Formicidae) remain almost unknown. The main objective of this work was to study the ground ant diversity in four main habitats of Iberá: grasslands, savannas, forests, and floating islands. Pitfall traps were used to characterize ground foraging ant assemblages, compare ant diversity among environments, and establish habitat associations. We also used bait traps, manual collections, and Winkler and Berlese extractors on the ground, vegetation, and litter strata to increase the species inventory. In total, 94 species in 30 genera were captured, representing the highest number of species reported from a survey of a protected area of Argentina. The richest genus was Pheidole Westwood with 23 species including three species reported for the first time in Argentina. The most common species was Solenopsis invicta Buren. Overall, the savanna was the richest and most diverse habitat with the highest number of exclusive species and functional groups. The grassland showed the highest number of rare species, but only half of the expected species were captured. The forest showed the lowest ant richness, diversity, and equitability, but one half of the species were exclusive to forest habitat. Generalized myrmicines were predominant and dominant in all habitats. Our findings indicate that habitat specialization could be an important factor determining the organization of ant assemblages in Iberá. The protection of each of these unique and threatened natural habitats of Argentina is needed to ensure the long-term preservation of their exclusive ant species.

Fire ant decapitating flies in the genus Pseudacteon were tested for their potential as hosts or vectors of two microsporidian pathogens of the red imported fire ant, Solenopsis invicta. Decapitating flies that attacked or were reared from S. invicta workers infected by Kneallhazia (=Thelohania) solenopsae or Vairimorpha invictae were tested for either pathogen by polymerase chain reaction (PCR) tests or visual examination for spores using phase microscopy. Three species of fire ant decapitating flies acquired the pathogen, Kneallhazia solenopsae. K. solenopsae was detected in 58% of pooled samples of Pseudacteon obtusus flies and 44% of pooled samples of Pseudacteon cultellatus that developed in K. solenopsae-infected fire ant workers. K. solenopsae was also found in 17% of pooled samples of field-collected Pseudacteon curvatus. In contrast, the microsporidium V. invictae was not detected in P. obtusus reared from V. invictae-infected S. invicta workers. Neither K. solenopsae nor V. invictae were detected in any of the hovering or ovipositing flies in the laboratory exposures, indicating no mechanical acquisition of the microsporidia occurred during oviposition activity. Greater than 92% of the P. obtusus that developed in K. solenopsae-infected ants survived and emerged as adults, thus indicating no detrimental effects of the microsporidium on pupal development and emergence. These results indicate that Pseudacteon decapitating flies may be able to vector K. solenopsae but not V. invictae among fire ants. Further tests are planned to determine if flies containing K. solenopsae are capable of transferring this pathogen either during oviposition or by being consumed by fire ant larvae.

This work describes the annual and daily activity patterns of two parasitoid fly communities of the fire ant Solenopsis invicta (Hymenoptera: Formicidae) in their native range in Argentina. Pseudacteon (Diptera: Phoridae) flies were censused monthly for 1 yr at two sites in northwestern Corrientes province. Additionally, parasitism rates of S. invicta colonies naturally attacked in the field by Pseudacteon flies are reported for the first time from its native habitat. In total, 4,528 flies (86.3% females) of eight Pseudacteon species were collected attacking ants in the field. Pseudacteon litoralis Borgmeier and Pseudacteon nocens Borgmeier represented 71-79% of female flies censused in both sites. Most species were active throughout the year, although abundances were variable over time and between sites. The highest occurrence peaks of flies were recorded in spring, whereas the lowest occurrence was in summer. Fly abundance was higher close to dusk, whereas species diversity was highest at midday. Relationships among species were established based on their activity patterns and genetic proximity. The presence and abundance of four species were explained by climatic variables, whereas two species may have inherited similar circadian rhythms from a common ancestor. Overall, the parasitism rate by the nine species recorded was very low (0.24%). The highest percentage of parasitized workers was found in spring (0.5%) and occurred within the most complex habitat (gallery forest). The highest parasitism rate per site and colony was also for this habitat in spring (1.16 and 2.81%, respectively). The highest rates of emergence were recorded for Pseudacteon nudicornis Borgmeier.

Studies were conducted to examine the phenology, geographic distribution, and host specificity of the Solenopsis invicta virus-1 (SINV-1). Two genotypes examined, SINV-1 and -1A, exhibited similar seasonal prevalence patterns. Infection rates among colonies of S. invicta in Gainesville, Florida, were lowest from early winter (December) to early spring (April) increasing rapidly in late spring (May) and remaining high through August before declining again in the fall (September/October). Correlation analysis revealed a significant relationship between mean monthly temperature and SINV-1 (p0.0005, r=0.82) and SINV-1A (p0.0001, r=0.86) infection rates in S. invicta colonies. SINV-1 was widely distributed among S. invicta populations. The virus was detected in S. invicta from Argentina and from all U.S. states examined, with the exception of New Mexico. SINV-1 and -1A were also detected in other Solenopsis species. SINV-1 was detected in Solenopsis richteri and the S. invicta/richteri hybrid collected from northern Alabama and Solenopsis geminata from Florida. SINV-1A was detected in S. geminata and Solenopsis carolinensis in Florida and the S. invicta/richteri hybrid in Alabama. Of the 1989 arthropods collected from 6 pitfall trap experiments from Gainesville and Williston, Florida, none except S. invicta tested positive for SINV-1 or SINV-1A. SINV-1 did not appear to infect or replicate within Sf9 or Dm-2 cells in vitro. The number of SINV-1 genome copies did not significantly increase over the course of the experiment, nor were any cytopathic effects observed. Phylogenetic analyses of SINV-1/-1A nucleotide sequences indicated significant divergence between viruses collected from Argentina and the U.S.

The microsporidian pathogen Vairimorpha invictae is being evaluated for release in the United States as a potential self-sustaining biological control agent for imported fire ants. We examined the host range of this pathogen at 5 sites in northern Argentina where Solenopsis invicta Buren fire ant colonies had high levels of infection (28-83%). At 3 sites near the city of Corrientes, we examined 509 non-Solenopsis ants from 61 collections, 12 genera, and 19 species with a polymerase chain reaction-based screening procedure. No V. invictae infections were detected in any of the samples. At 2 sites near San Javier in Santa Fe Province, 350 km to the south, we screened another 438 non-Solenopsis ants from 44 baits, 4 genera, and 4 species, again with no infections. At the Corrientes sites, we also examined 235 non-ant arthropods from 10 orders, 43 families, and more than 80 species. None were infected with V. invictae. The results of this study indicate that, in its native South American range, V. in...

Twenty-two species of Pseudacteon flies (Diptera: Phoridae) are known to attack fire ants (Solenopsis spp.) in Argentina, Brazil, Bolivia, and Paraguay, but none are known in Chile. Surveys were conducted in central Chile and at similar latitudes in western Argentina to detect the presence of fire ants and parasitoid flies and to determine their relationship. Flies and fire ants were much more common and abundant in Argentina. In total, 100 colonies of four fire ant species were found at 63.6% of the sites surveyed. In contrast, only six colonies of one species, Solenopsis gayi (Spinola), were found at 4.7% of the sites surveyed in Chile. Our survey includes the first record of five parasitic fly species in central western Argentina and a new host, Solenopsis quinquecuspis Forel. The large form of Pseudacteon obtusus Borgmeier was found attacking S. gayi in Chile, which is the first record in that country, and the first record on this host species. The southern-most and western-most records were established for fire ant-decapitating flies. Mitochondrial DNA (mtDNA) indicates that S. gayi is genetically closer to the Argentine fire ants (saevissima-group) than the North American S. geminata-group. However, S. gayi venom alkaloid composition is similar to S. geminata-group, whereas cuticular hydrocarbon composition has characteristics of both groups. Analysis of mtDNA from the collected flies supports the monophyly of P. obtusus and suggests that the Chilean population is similar to populations in eastern Argentina. The presence of P. obtusus in Chile could be explained by immigrant parasitized fire ant species from Argentina or by an accidental introduction.

The ant genus Wasmannia is endemic to the Neotropics, with 10 species occurring within the presumptive native range for the genus from Mexico to Argentina. Only the little fire ant, Wasmannia auropunctata is widely distributed being present from central-eastern Argentina to Bermuda, and has become infamous due to its recent worldwide expansion and status as an invasive pest. The objective of this work was to study the systematics and distribution of Wasmannia in its southern limit of distribution in Argentina. Out of the three species reported so far for Argentina, only W. auropunctata was found to be widely distributed, but abundant only in disturbed habitats mostly in the Northeast. Herein, the distribution of Wasmannia auropunctata is extended and its queen and male castes are redescribed, along with descriptions of gynandromorphs (specimens with left side of the head similar to a male and right side similar to a queen). Wasmannia sulcaticeps and W. williamsoni are much less common and widespread. W. sulcaticepsis mostly found in mountain forests in northwestern Argentina, whereas W. williamsoni is only found in shrublands and grasslands in central eastern Argentina, and most frequently in mountain grasslands. Both species overlap with W. auropunctata, which is more common in the lowlands, between approximately 400 and 1000 m elevation. The queen of W. williamsoni is described and queen and male of W. sulcaticeps are redescribed. A new species, Wasmannia longiseta n. sp. Cuezzo and Calcaterra, recently found in northeastern Argentina is described based on worker morphology. Wasmannia rochai is recorded for the first time in Misiones, extending its distribution range from São Paulo (Brazil) to Misiones in northeastern Argentina. A key to the worker caste is provided. A cladistic analysis based on discrete and continuous morphological characters is presented as a first attempt to clarify the phylogenetic relationships between the known species of Wasmannia. Fil: Cuezzo, Fabiana del Carmen. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales E Instituto Miguel Lillo. Instituto Superior de Entomología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Calcaterra, Luis Alberto. Fundación Para El Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Chifflet, Lucila. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Follet, P. A.. Pacific Basin Agricultural Research Center; Estados Unidos

We describe the ant fauna of Iguazú National Park (INP), a region of high biodiversity andendemism in northeastern Argentina that includes the southernmost protected area ofthe Atlantic Forest (AF). Ants were sampled over seven periods from 1998 to 2011 usinga variety of techniques. We also surveyed museum collections and the scientific literatureto obtain additional records of ants from INP. In addition to providing a species list, wecompare ant composition of INP to other sites in the Upper Paraná, Serra do Mar CoastalForest and Araucaria ecoregion of AF. A total of 172 ant species belonging to 56 genera arereported; 56 species are new records for Misiones Province and 39 species are reportedfrom Argentina for the first time. Alto Paraná and Canindeyú departments in Paraguaypresent the most similar ant fauna to INP. Serra da Bodoquena in Brazil and Pilcomayoin Argentina showed higher similarity with the Upper Paraná AF ecoregion, despite thatSerra da Bodoquena is composed of a mix of ecoregions. Ant diversity was lower in UpperParaná than in Serra do Mar Coastal Forest ecoregion. This difference may result fromhigher primary productivity and a greater altitudinal variation in the coastal region. Fil: Hanisch, Priscila Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; Argentina Fil: Calcaterra, Luis Alberto. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Leponce, M.. Royal Belgian Institute of Natural Sciences. Aquatic and Terrestrial Ecology unit; Bélgica Fil: Achury, R.. University of Illinois at Urbana; Estados Unidos Fil: Suarez, A. V.. University of Illinois at Urbana; Estados Unidos Fil: Silva, R. R.. Museu Paraense Emílio Goeldi; Brasil Fil: Paris, Carolina Ivon. Universidad de Buenos Aires; Argentina

The South American big-headed ant Pheidole obscurithorax was first found in North America in Mobile, Alabama in 1949. Since then, this species has also been recorded in Florida, Georgia, Mississippi, and Texas. We compiled and mapped published and unpublished specimen records of P. obscurithorax from >170 sites in South America and the US to evaluate the current geographic range of this species and its possible future spread. We documented the earliest known records for nine geographic areas (South American countries and US states). Site records of P. obscurithorax ranged 27.5 degrees of latitude (from 6.7°S to 34.2°S) in South America, and 3.5 degrees of latitude (from 28.0°N to 31.5°N) in North America. It may be that the North American populations of P. obscurithorax have a fairly narrow range of climatic tolerances. Earlier genetic analyses of native and exotic populations of P. obscurithorax found that the North America populations appear to originate from a single introduction from a population most closely related to native study populations from a stretch along the Paraná River in Argentina from Resistencia (27.5°S) to Santa Fe (31.6°S). This latitudinal range matches the current latitudinal range of P. obscurithorax in North America. Alternatively, the much greater latitudinal range of P. obscurithorax in South America suggests that exotic populations of P. obscurithorax may have potential for much additional expansion in North America and beyond. In South America, P. obscurithorax has a similar native range as the invasive fire ant Solenopsis invicta. In the North America, exotic populations of P. obscurithorax may spread like S. invicta has, across the southeast of the US and into the West Indies. Fil: Wetterer, James K.. Mississippi State University; Estados Unidos Fil: MacGown, Joe A.. Mississippi State University; Estados Unidos Fil: Calcaterra, Luis Alberto. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

The exploration for the fire ant diseases Vairimorpha invictae Jouvenaz and Ellis (Microsporidia: Burenellidae) and Thelohania solenopsae Knell, Allen, and Hazard (Microsporidia: Thelohaniidae) was conducted from 2001 to 2005 in Argentina, Paraguay, Chile, Bolivia, and Brazil. A total of 2,064 colonies were sampled from 262 sites. Three sites with high prevalence of pathogens were monitored periodically for the persistence of the infections. V. invictae occurred at 12% of the sites and in 10% of the colonies. Except for one infected colony in Bolivia, its distribution was restricted to the eastern part of the region surveyed. The highest occurrence was in Santa Fe Province. T. solenopsae presented a much wider distribution. It occurred at 25% of the sites and in 13% of the colonies. The highest occurrence was in Buenos Aires Province. This is the first report of T. solenopsae in the northwest, in the west, in central Argentina, and in Bolivia, and infecting S. interrupta (Santschi). Simultaneous infections were found at 4% of the sites and in 2.2% of the colonies. The periodical examination revealed high infection levels in most occasions. The prevalence of T. solenopsae ranged from 10 to 90% of the colonies, V. invictae from 0 to 60%, and dual infections from 0 to 50%. Each microsporidium exhibited a characteristic enzootic/epizootic wave. Successive epizootic levels observed in both infections provide a more constant pressure against fire ant populations. These diseases are promising classical biological control agents of the imported fire ants in the United States.

The distribution and abundance of fire ant decapitating flies (Diptera: Phoridae: Pseudacteon Coquillett) were studied in three regions of southern South America, primarily from September 2002 to September 2004. A total of 2,421 flies belonging to 14 Pseudacteon species were found at 51% of the 662 fire ant mounds examined at 125 collecting sites. Flies occurred in a variety of habitats at altitudes from sea level to 2,280 m. Pseudacteon obtusus Borgmeier (large form) was found at the highest altitude and at the most western longitude. Flies were active between 16 and 37°C, 20 and 90% RH, and 0 and 11.6 km/h wind speed. Pseudacteon curvatus Borgmeier showed the highest abundance and one of the broadest geographical distributions. Pseudacteon tricuspis Borgmeier, P. litoralis Borgmeier, the large form of P. obtusus, P. nudicornis Borgmeier, and P. nocens Borgmeier also were widely distributed. These species seem to be the most generalized within saevissima-group. Pseudacteon solenopsidis Schmitz w...

The fire ant Solenopsis invicta is a significant pest that was inadvertently introduced into the southern United States almost a century ago and more recently into California and other regions of the world. An assessment of genetic variation at a diverse set of molecular markers in 2144 fire ant colonies from 75 geographic sites worldwide revealed that at least nine separate introductions of S. invicta have occurred into newly invaded areas and that the main southern U.S. population is probably the source of all but one of these introductions. The sole exception involves a putative serial invasion from the southern United States to California to Taiwan. These results illustrate in stark fashion a severe negative consequence of an increasingly massive and interconnected global trade and travel system.

Abundance of the workerless parasitic ant Solenopsis daguerrei (Santschi) in fire ant populations was surveyed in southern and southwestern Brazil, eastern, central, and northern Argentina, western and northern Uruguay, central Paraguay, and Bolivia from 1974 to 1996. A total of 12,180 fire ant colonies was sampled from 726 collecting sites for the presence of adults or queens, or both, of the parasitic ant. The presence of the parasite in fire ant colonies within the area surveyed was very low. In Argentina, S. daguerrei occurred in the provinces of Buenos Aires, Santa Fe, and Entre Rios, in 1.4–7.0% of the colonies. In Brazil, the areas of Dourados, Campo Grande, and Rochedo, Mato Grosso do Sul contained 1–6.2% of parasitized colonies. In Uruguay

Evolution may improve the invasiveness of populations, but it often remains unclear whether key adaptation events occur after introduction into the recipient habitat (i.e. post-introduction adaptation scenario), or before introduction within the native range (i.e. prior-adaptation scenario) or at a primary site of invasion (i.e. bridgehead scenario). We used a multidisciplinary approach to determine which of these three scenarios underlies the invasion of the tropical ant Wasmannia auropunctata in a Mediterranean region (i.e. Israel). Species distribution models (SDM), phylogeographical analyses at a broad geographical scale and laboratory experiments on appropriate native and invasive populations indicated that Israeli populations followed an invasion scenario in which adaptation to cold occurred at the southern limit of the native range before dispersal to Israel. We discuss the usefulness of combining SDM, genetic and experimental approaches for unambiguous determination of eco-evolutionary invasion scenarios. Fil: Rey, Olivier. Institut National de la Recherche Agronomique; Francia Fil: Estoup, Arnaud. Institut National de la Recherche Agronomique; Francia Fil: Vonshak, Merav. Universidad de Tel Aviv; Israel Fil: Loiseau, Anne. Institut National de la Recherche Agronomique; Francia Fil: Blanchet, Simon. Centre National de la Recherche Scientifique; Francia Fil: Calcaterra, Luis Alberto. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Chifflet, Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Rossi, Jean Pierre. Institut National de la Recherche Agronomique; Francia Fil: Kergoat, Gaël J.. Institut National de la Recherche Agronomique; Francia Fil: Foucaud, Julien. Institut National de la Recherche Agronomique; Francia Fil: Orivel, Jérôme. Centre National de la Recherche Scientifique; Francia Fil: Leponce, Maurice. Royal Belgian Institute Of Natural Sciences; Bélgica Fil: Schultz, Ted. Smithsonian Institute Natural Museum Of Natural History; Estados Unidos Fil: Facon, Benoit. Institut National de la Recherche Agronomique; Francia

We review the fire ant research conducted by the ARS-South American Biological Control Laboratory (SABCL) since 1987 to find a complex of natural enemies in southern South America and evaluate their specificity and suitability for field release as self-sustaining biological control agents. We also include those studies conducted by the ARS-Center for Medical, Agriculture, and Veterinary Entomology in the United States with the SABCL collaboration. Ecological and biological information is reported on local fire ants and their microsporidia, nematodes, viruses, phorid flies, eucharitid wasps, strepsiptera, and parasitic ants. Their biology, abundance, distribution, detrimental effect, field persistence, specificity, and phenology are discussed. We conclude that the objectives of the ARS program in South America are being achieved and that the pioneering studies have served to encourage further investigations in the United States and other countries and advanced the implementation of biological control programs to decrease imported fire ant densities and damage. Still, several promising organisms should be further investigated for eventual field release in the near future.

Since the 1960s, the workerless (permanent) parasitic ant Solenopsis daguerrei (Santschi) has been considered part of a complex of potential candidates for introduction into the United States for the biological control of the red and black imported fire ants, Solenopsis invicta Buren and S. richteri Forel respectively (Lofgren et al. 1975, Jouvenaz 1990, Wojcik 1990). Pioneering work on S. daguerrei was conducted in Uruguay and Argentina by Silveira Guido et al. (1973; unpublished reports). More recent studies have been conducted at the USDA-ARS-South American Biological Control Laboratory (SABCL) since 1988 and more intensively since 1995. Studies included records on its occurrence and abundance in southern South America (Briano et al. 1997) and field and laboratory observations on its specificity, biology and behavior (Calcaterra et al. 1999, 2000, 2001). Also, many fire ant colonies from Argentina parasitized with S. daguerrei were shipped into quarantine at the USDA-ARSCenter for Medical, Agricultural, and Veterinary Entomology (CMAVE), Gainesville, FL, where complementary studies were conducted (unpublished information). Although detrimental effects on fire ants were reported in Argentina (Calcaterra et al. 1999), further progress on the project was not achieved because of (1) the difficulty in rearing S. daguerrei under laboratory conditions and (2) the failure to introduce and establish the parasite into new host colonies. A number of attempts to introduce and propagate S. daguerrei in laboratory and field host colonies were conducted in Argentina from 1996 to 1999 following different approaches. Some of this work was reported by Calcaterra et al. (2001). Although some tests showed limited success, S. daguerrei did not establish permanently in any of the target host colonies. Despite this failure, we believe that reporting the different approaches used in our studies will contribute to future research efforts. Parasitized and nonparasitized colonies used in the tests were mostly multiple-queen colonies of S. richteri collected in four areas of Buenos Aires Province: (1) San Eladio (60 km W of Buenos Aires), (2) Saladillo (180 km SW of Buenos Aires), (3) Mercedes (100 km W of Buenos Aires), and (4) Suipacha (125 km W of Buenos Aires). The colonies were excavated in the field, brought to the laboratory in 10-liter buckets dusted with talc, separated from the soil by flotation (Banks et al. 1981) and placed in trays. The basic approaches used in the laboratory tests were: #1) Transference of queens: Target host colonies were fragmented into microcolonies (n = 34) composed of one host queen, 50 workers and approximately 1 gr. of brood. These microcolonies were maintained in artificial nests (Bishop et al. 1980) in plastic rearing trays (40 x 25 x 7 cm) coated with Fluon? and fed adult house flies and/or canned Vienna sausage. A water source was always present. One active S. daguerrei queen separated from a parasitized colony was transferred to each microcolony. For about one month, the colonies were kept at different temperatures as follows: 10?C (five colonies), 10-15?C (eight colonies), 15?C (11 colonies), and 30?C (10 colonies). In five of these colonies kept at 30?C, the S. daguerrei queens were sprayed before transference with an extract of macerated workers from the target (receptor) host colony. The tests were monitored daily for the presence of the parasite in the receptor microcolonies. #2) Transference of sexuals: Similarly, target host colonies were fragmented into microcolonies (n = 22) as above and kept in trays at 15 'C. A total of 92 sexuals (alates) of S. daguerrei (3-9 per microcolony) was transferred and monitored daily. #3) Transference of pupae: Test 1. Target host colonies were fragmented (n = 6) as above and kept at 150C. Six pupae of S. daguerrei were transferred to each microcolony. Test 2. Host colonies were fragmented into microcolonies (n = 4) composed of six host queens and 1 gr. of workers and maintained between 19-30?C. A total of 200 pupae of S. daguerrei was transferred to the microcolonies (six pupae per colony every 3-4 days for three weeks). #4) Entire colonies in contact: Test 1. A small plastic tray (40 x 25 x 7 cm, coated both inside and outside with Fluon?) with a parasitized colony was placed in a larger tray (50 x 40 x 12 cm) with a parasite-free colony. The colonies were monitored daily to observe the short flights of S. daguerrei sexuals into the larger tray and their survival. Test 2. Two trays (50 x 40 x 12 cm), the first with a parasitized colony and the second with a parasite-free colony were interconnected through plastic tubes (1 cm in diameter) to a third

Despite the widespread impacts invasive species can have in introduced populations, little is known about competitive mechanisms and dominance hierarchies between invaders and similar taxa in their native range. This study examines interactions between the red imported fire ant, Solenopsis invicta, and other above-ground foraging ants in two habitats in northeastern Argentina. A combination of pitfall traps and baits was used to characterize the ant communities, their dominance relationships, and to evaluate the effect of phorid flies on the interactions. Twenty-eight ant species coexisted with S. invicta in a gallery forest gap, whereas only ten coexisted with S. invicta in a xerophytic forest grassland. S. invicta was the most numerically dominant species in the richest and complex habitat (gallery forest); however it performed better as discoverer and dominator in the simpler habitat. S. invicta was active during day and night. In spite of its poor capacity to discover resources, S. invicta showed the highest ecological dominance and the second-best behavioral dominance after Camponotus blandus. S. invicta won 78% of the interactions with other ants, mostly against its most frequent competitor, Pheidole cf. obscurithorax, dominating baits via mass recruitment and chemical aggression. P. cf. obscurithorax was the best food discoverer. S. invicta won 80% of the scarce interactions with Linepithema humile. Crematogaster quadriformis was one of the fastest foragers and the only ant that won an equal number of contests against S. invicta. The low presence of phorid flies affected the foraging rate of S. invicta, but not the outcome of interspecific interactions. This study revealed that the red imported fire ant ecologically dominated other terrestrial ants in its native range; however, other species were able to be numerically dominant or co-dominant in its presence.

One possible mechanism for interspecific transfer of Wolbachia is through the intimate contact between parasites and their hosts. We surveyed 10 species of fly parasitoids ( Pseudacteon spp.) and one inquiline social parasite, Solenopsis daguerrei , for the presence and sequence identity ( wsp gene) of Wolbachia . Two Wolbachia variants infecting S. daguerrei were identical to known variants infecting the two common ant host species, Solenopsis invicta and Solenopsis richteri , suggesting possible transfers of Wolbachia between this parasite and their hosts have occurred. Our data also revealed an unexpectedly high diversity of Wolbachia variants within S. daguerrei : up to eight variants were found within each individual, which, to our knowledge, is the highest reported number of Wolbachia variants infecting a single individual of any host species.

The parasitic ant Solenopsis daguerrei (Santschi) has been reported as an inquiline of fire ants in South America. It lacks a worker caste, so all adults are reproductive males and females. The parasite queens and occasionally some virgin females attach themselves to the host queens, and divert resources from them. The fire ant workers tend S. daguerrei in a manner similar to their own mother queens (Bruch 1930). The host workers also feed and maintain the brood of S. daguerrei. According to Silveira-Guido et al. (1973) this parasite inhibits the egg production of the fire ant mother queen, thus causing the ant colony to collapse and eventually die out. Recently it was reported that multiple-queen colonies of fire ants parasitized with S. daguerrei have fewer queens than non parasitized ones (Calcaterra et al. 1999). Because of these findings, this parasitic ant is a candidate for introduction for the biological control of imported fire ants in the United States and is under quarantine conditions at the USDA-ARS CMAVE, Gainesville, FL. However, before S. daguerrei can be released from quarantine, its host specificity must be determined. Surveys on fire ant natural enemies in South America revealed that S. daguerrei has been found in Argentina, Uruguay, and Brazil, in colonies of S. richteri Forel, S. invicta Buren, S. saevissima F. Smith, and S. macdonaghi Santschi (Silveira-Guido et al. 1973, Briano et. al. 1997, Pesquero et al. 1998, Calcaterra et al. 1999). Here we report a new host species for S. daguerrei. As part of the study of the specificity of S. daguerrei, a field host range survey was conducted in San Eladio (60 km W of Buenos Aires), Argentina, the only place where S. daguerrei has been found consistently since 1995. This area had the highest abundance (7% of fire ant colonies) of S. daguerrei recorded in South America to date (Briano et al. 1997). The surveys were conducted from December 1996 to May 1997 and from November 1997 to May 1998 and consisted in walking through the pastures to visually detect the ant colonies. When an ant nest was found, it was excavated, scattered on the ground, and thoroughly examined for S. daguerrei adults. Some colonies were excavated and put into 10-liter buckets for separation in the laboratory by flotation (Banks et al. 1981). The floated colonies were put in rearing trays (40 by 30 by 15 cm) and examined later. Alcohol samples were kept of most ant species found. Samples of 34 parasitized fire ant colonies were preserved in hexane to confirm their identification by gas chromatography analysis of cuticular hydrocarbons and venom alkaloids (Vander Meer & Lofgren 1988). Voucher samples were deposited at the USDA-ARS, SABCL collection and at the USDA-ARS, CMAVE, Gainesville, FL. We sampled a total of 4,316 ant colonies of 9 different species in 4 subfamilies, however 96% of them were fire ants. Other species examined were: Pheidole bergi Mayr, Acromyrmex lundi Gu6rin, A. ambiguus Mayr, Camponotus punctulatus Mayr, Neivamyrmex pertyi Shuckard, Linepithema humile Mayr, and Brachymyrmex sp. S. daguerrei was found exclusively in 161 colonies of fire ants (Table 1). Taxonomic studies revealed that 95% of the parasitized colonies corresponded to S. richteri. The